Art of lubrication



Patented May 21,1946

' ART OF LUBRICATION Willard L. Finley, Sparta, Ill., and James H..Kirk,Hammond, Ind., assignors to Sinclair Refining Company, New York, N. Y.,a corporation of Maine No Drawing. Original application August 19,

1941, Serial No. 407,440. Divided and this application July 23, 1943,Serial No. 495,890

3 Claims.

from 4 to 6 carbon atoms and iso alkyl esters of.

salicylic acid of which the alkyl group contains from 6 to 18 carbon'atoms. In compounded lubricating oils containing these-mixed salts, themixed salts are advantageously incorporated in amounts insufllcientmaterially to alter the normally liquid character of the petroleumlubricating oil base. This application is a division of our copendingapplication Serial No. 407,440, filed August 19, 1941, upon which PatentNo. 2,348,461 was granted May 9, 1944. The trend of development ininternal combustion engines has imposed increasing burdens upon the oilsused for their lubrication, particularly with rspect to the operatingtemperatures and pressures. Extreme requirements in both of theserespects are represented by the Diesel type of engines and superchargedaircraft engines. The useful operating life of a lubricating oil, insuch severe services, is determined in large measure by its thermalstability and by its physical capacity to continue iunctioning as alubricant at the high temperatures and pressures encountered. The use ofspecial alloy bearing metals, to permit the use of increased bearingpressures and consequently smaller bearing surfaces, adds to theseburdens both in that such metals, in contact with the oil, frequentlytend to accelerate degradation of the petroleum lubricating oil base andin that lubricating oils and lubricating oil compositions which have therequisite properties in other respects frequently tend to be corrosivewith respect to such metals. One measure of thermal stability isresistance to oxidation. Oxidation promotes either the formation ofsludge or the formation. of acids corrosive to bearing metals, or both.To have any real meaning, this measure of thermal stability mustbe-applied under conditions of service since, for example,-bearingmetals may promote oxidation. In another aspect, thermal stability isdetermined not only by the extent of oxidation or decomposition but alsoby the character of the products of such decomposition or oxidation andby the extent salts ofand location, within the engine, of deposits ofsuch products, sludge, coke andresinous varnishlike materials, forexample.

In previous applications, Serial No. 368,992, filed December 7, 1940,and Serial No. 407,002, filed August 15, 1941, by Willard L. Finley, oneof the co-applicants herein, the compounding of etroleum lubricatingoils with calcium salts of alkyl esters of salicylic acid includingthe'normal alkyl esters andthe iso alkyl esters has been described. Theaddends described in those applications function as strong anti-oxidantseffective to inhibit, over prolonged induction periods, the rate ofoxygen absorption at elevated temperatures and thus to limit anycorrosive tendencies of the lubricating oil compositions with respect tobearing metals, to render deposits of sludge and carbon within theengine soft and friable rather than hard and coherent, and to act as asolvent 0 for sludge formed and thus to disintegrate and remove anydeposits of sludge'and carbon as an incident of normal engine operation.

' These valuable properties of the calcium salts of alkyl esters ofsalicylic acid, however, are

rapidly impaired or even destroyed by thepresence in the lubricating oilcomposition, under service conditions, of metallic soaps such as thoseformed by corrosion of bearing metals through reaction with acidoxidation products of the lubricating oil composition. The use of alkylphenol sulfides, including polymers and polysulfides, as addends in thecompounding of petroleum lubricants has been described. Such addendshave little if any direct effect as anti-oxidants, and

85 they tend to accelerate sludge formation, but they do function toprotect metals with respect to corrosion, to inhibit the solution ofmetals in the lubricating oil composition, to precipitate or otherwiseto deactivate any dissolved metal and particularly to minimize thepro-oxidant eiiect of any dissolved metal. We have now combined thedesirable functions of these two types of addends to secure newadvantages from the combination and to avoid the disadvantages andlimitations of either used alone.

We have found that such alkyl phenol sulfides and such alkyl esters ofsalicylic acid can be combined with lime to form mixed salts, thecompositions of our invention, which are powerful anti-oxidants, whichinhibit corrosion or solution of metals, which deactivate dissolvedmetals, which are powerful detergent-dispersion agents, which inhibitviscosity rise and which contribute tothe film strength of compoundedpetroleum lubricating oils in which they are incorporated.

. The octyl ester of salicylic acid, for example, may

be represented by the following formula:

The amyl phenol polysulfide, for example, may be represented by thefollowing formula:

(IHI (illl ClsUu (351111 which may be' represented by the followingformula:

4 oC lluC-aOOCO I Q O I I C5111 Ctllu The mixed salts illustrated by theforegoing type formulas are the compositions of our present ine vention.These mixed salts can be formed by reaction between the alkyl phenolsulfide and either the neutral or the basic calcium salt of the alkylester of salicylic acid. If the reaction is between the basic salt andthe alkyl phenol sulfide, water is liberated; if the reaction is betweenthe neutral salt and the alkyl phenol sullide, an alkyl ester isliberated. Or, these mixed salts can be formed directly by reacting limewith a mixture of the alkyl ester of salicylic acid and the alkyl phenolsulfide. The reaction is with advantage carried out in a solvent, andlubricating oil compatible with the compounded lubricating oil in whichthe mixed salt may ultimately be incorporated is an advantageousreaction medium. The reaction is with advantage carried out with asufficient excess of the alkyl ester of salicylic acid so that theaddend composition, and the petroleum lubricating oil composition inwhich it is incorporated, will include a proportion of the calcium saltof. the alkyl ester of salicylic acid somewhat larger than theproportion of the mixed calcium salt of the alkyl phenol sulfide and thealkyl ester of salicylic acid. The excess of the calcium salt of thealkyl ester of salicylic acid maybe in the form of the neutral salt or amixture ofthe neutral and basic salts. The reaction is with advantagecarried out at a temperature below that at which substantial conversionof the compound in which the calcium replaces phenolic hydrogen tocompound in which the calcium replaces carboxylic hydrogenor alkylgroups takes place. At maximum temperatures of about 280 F. thisconversion is negligible but at temperatures upwards of about 300 F. itproceeds with increasing rapidity. Thetotal proportion of calcium saltsof the alkyl esters of salicylic acid in a compounded lubricating oilcontaining the compositions of our invention may approximate, withadvantage, from about 1% to about 5% .by weight on the compoundedlubrieating oil, and of this the mixed calcium salts of the alkyl estersof salicylic acid and the alkyl phenol sulfides may, with advantage,approximate a proportion equivalent to from about 0.2% to about 0.5% ofthe alkyl phenol sulfide.

While the mixed calcium salts of our invention can be prepared as aseparate product, for example, in solvents such as benzene or toluene orpetroleum hydrocarbons, we have found it advantageous to produce thesecompositions by reaction in the petroleum lubricating oil base of thecompounded lubricating oil in which it is to be incorporated. Forexample, we add 1%, 2%, 3% or somewhat more of the neutral calcium saltof the alkyl ester of salicylic acid, or of a mixture of the neutral andbasic calcium salt of the alkyl ester of salicylic acid, to thepetroleum lubricating oil base, or a portion of it, then add from about0.2% to about 0.5% of the alkyl phenol sulfide to this mixture and thendehydrate the composite at a temperature not exceeding about 280 F.under a vacuum if necessary. Or, for example, we add the equivalentproportions of the alkyl ester of salicylic acid and of the alkyl phenolsulfide and the reacting proportion, or somewhat more, of lime ascalcium hydroxide to the petroleum lubricating oil base, or a portion ofit. and then dehydrate the composite in the same manner. The followingcompounded lubricating oils containing the composition of our inventionas addends will illustrate the application of the invention:

I II III Gravity, API 18.4 26.8 27.0 Flash, "F 420 430 430 Fire, F 480490 490 Viscosity at F 1666 565.4 600. 2 Viscosity at 210 F 80. 9 07. 739. 5 Viscosity indcx... 09. 3 09. l lour, "F 0 5 0 Carbon residue(ash-free), percent..." .00 1.19 1.26 sh 0.67 0.59 0. 61 Color NPA 7(4}5) 7(4}) In the foregoing compounded lubricating oils, the addendsembodying the compositions of our invention consisted of the reactionproduct .of a mixture of the neutral and basic calcium salts of the isooctyl ester of salicylic acid in which the basic salt comprised fromabout one-fifth to about one-half of the mixture and tertiary amylphenol sulfide in polymerized form and containing polysulfide sulfur. InExample I, the reaction product of 4% of the calcium salt of the isooctyl ester of salicylic acid and 0.25% of the tertiary amyl phenolsulfide wasincorporated in a pale oil blend derived from a South Texascrude. Examples 11 and III were a Pennsylvania motor oil (SAE 30)containing the reaction products, respectively, of 4% 0f the calciumsalt and 0.5% of the sulfide and 4% of the calcium salt and 0.25% of thesulfide. All of the compounded lubricating oils of the foregoingexamples were basic in reaction.

compounded as just described, lubricating oil compositions, afteraddition of 0.01% FezOa as ing from nothing up to 0.005 gram under testconditions (the "Underwood oxidation test") such that the loss from thesame lubricating oil base, without the addends but with the addition ofthe same proportion of the same pro-oxidant. ranged from 1.454 grams to1.894 grams with cadmium silver bearing metal. Similar comparisons,based on identical tests, have shown that our improved results are notsecured with either the calcium salt of the alkyl ester of salicylicacid 01' the alkyl phenol sulfide used alone, uncombined. Petroleumlubricating compositions containing the mixed calcium salts of ourinvention also exhibit a marked increase in sludging time as indicatedby the Indiana oxidation test." For-example, with a petroleum 011 basesuch'as that of Example I,

the sludging timewas increased from 22.5 hours to 35 hours byincorporating the reaction products of 1% of the calcium salt and 0.5%of the sulfide and to 60 hours by incorporating the reaction products of3.5% of the calcium salt and 0.5% of the sulfide. Similarly, with apetroleum oil base such as that of Example 11 and III, the

sludging time was increased from 200 hours to I 365 hours byincorporating the reaction products illustrated by the followingtabulated results of identical comparative tests (the "Underwoodoxidation test) applied to Sample A, an uncompounded oil of the typeused in the previous Example I, and to Sample 13, the same base oilcontaining the reaction products of 3.5% of the calcium salt and 0.5% ofthe sulfide. To each sample 0.01% or FezOa as iron naphthenate was addedas a pro-oxidant.

Sample A Sample B Oil tests before oxidation:

Carbon residue, percent 0. l2 1. 39 Vlscosi at 210 F 79 84 Neutral tionNo. method A-.-" 0. M6 Alkaline Oil tests after 5 hours:

Carbon residue, percent l. 38 1. 41 Visooei at 210 F 103 86 Neutraletion No. method A-.-" 2.46 0. 20 Neutralization No. method B-.. 2. 760. Beeringrcorroei n Cd-Ag), fms" 0. 622 0. 001

A. 8. M. nap the inso uble,

fiercent l. 46 0. 02 C Ch insoluble, percent 4 0. 08 0. 01 Oil testsalter 10 hours:

Carbon residue, percent 2. 84 1. 51 Viscosit at 210 F 137 88 Neutralnation No. method A".-. 6.03 0.80 Neutralization No. method B..-.- 6.000. 85 Bearinfi corrosion (Cd-Ag), gms-- 1.464 0.001 A. S. M. naphthainsoluble,

eroent 3. 52 0. 08 C Ch insoluble, percent 0.09 0. (I) l The highsolvent, or detergent-dispersion, capacity of the compositions of ourinvention when incorporated in a compounded petroleum lubrieating oil,moreover, imparts to the lubricating oil' a marked capacity to suppressring sticking and excessive piston deposits and consequently to minimizering and cylinder wall wear and to reduce any tendency toward scufllngof'pistons,

in the presence of the bearing metals under severe,

mixed calcium salts of the present invention in compounded lubricatingoils, with respect to diminished carbon or like deposits within thecylinders of internal combustion engines and bearing corrosion losses,are illustrated by the .following tabulated results of comparative tests(Bus engine sludging test) wherein the oil is subjected to conditionsclosely approximating those encountered in actual use. The apparatusused in these tests consists of a metal box or sump adapted to hold apool of oil which is heated by an oil bath in which the box issuspended. The box is provided with a cover heated by a lead bath. Arotary paddle wheel is supported within the box so that inrotating theblades thereof dip into the oil pool and throw the oil onto the sidesand cover of the box and also onto an alloy bearing sus-- pended in thebox abovethe surface of the pool of oil. The cover and upper portion ofthe sides of the box are partially shielded from the oil thrown from thepaddle wheel by a screen of 30- mesh iron screen wire.

In carrying outthis test, the temperature of the oil in the sump ismaintained at 250 F., and the temperature of the lead bath is maintainedat500 F. The paddle wheel is rotated at 750 R. P. M. and air i blownthrough the chamber at a rate of 1 cubic foot per minute. The test isdivided into 2 periods of 150 hours each. In

' starting the test, 2 liters of oil are placed in the sump. At the endof the first period, the oil is drained from the sump and new oil addedtogether with 10% of the oil used in the first period of the test. Atthe end of each period the amount of corrosion of the bearing wasdetermined by the Sample 0 Sample D Condition at end 01300 hour test:

Deposit on cover, 65.9----'. 0.4.

was.

Appearance oicover. Covered with coke.. Essential! clear.

Condition of sump-. Walls varnished.. o v

Condition atoll--." Bright and viscous" Bright and not vis- Beeringlosemga: I

15o hour's... no 10.

300 hours- 67 13.

The stability of a petroleum lubricating oil as represented by theoxygen absorption test is great- 1y improved by the incorporation in theoil of the mixed salts of the present invention. This i illustrated bythe following tabulations of comparative results in which Sample E is anuncompounded Pennsylvania motor oil (SAE 30) of the type used inExamples 11 and III and Sample F is the same oil having compoundedtherewith the reaction products of, 1% of the calcium salt and 0.25% ofthe sulfide. The results of the tests are reported in terms of number orminutes required for the absorption oi" the indicated cubic centimetersof oxygen at normal temperature, and pressure per grams of oil.Eachsample was tested in the presence of copper-lead alloy bearing andunder comparable conditions.

0. c. of oxygen/100 grams of oil Sample E Sample F Min. Mim

ing oil, consisting of a pale oil blend derived from a South Texascrude, containing the reaction.

products of 4% of the calcium salt and 0.25% of the sulfide, hassatisfactorily lubricated the Diesel engine of a large streamlinelocomotive for a distance upwardsof- 65,000 miles without change ofcrankcase oil.

We claim:

1. The mixed calcium salts of alkvl phenol sulfides of which the alkylgroups contain from four to six carbon atoms and alkyl esters ofsalicylic acid of which the alkyl groups contain from six I to eighteencarbon atoms.

2. The mixed calcium salts of tertiar alkyl phenol sulfides of which thealkyl groups contain from four to six carbon atoms and iso alkyl estersof salicylic acid of which the alkyl groups contain from six to eighteencarbon atoms.

3. A mixed calcium salt of tertiary amyl phenol sulfide and iso-octylester of salicylic acid.

